This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We have used a label-free quantitative nanoESI-HPLC mass spectrometric method to perform comparative proteomics analysis on the urine from control rats and rats bearing 4-hydroxybutyl(butyl)nitrosamine induced bladder tumors. In this study the urinary proteins from control animals (n = 10) and from those with palpable bladder tumors (n = 10) were digested sequentially with endoprotease Lys C and trypsin after reduction and alkylation. The peptides were separated with nanoflow- reversed phase HPLC, ionized with nanospray ionization, and analyzed with a hybrid linear quadrupole Fourier transform ion cyclotron mass spectrometer (FT-MS). Parent mass scans were acquired over a 2 h linear gradient of acetonitrile for each of the 20 samples. The mass spectra from the control and tumor-bearing groups were aligned and the individual accurate mass signals were quantified using Rosetta ElucidatorTM software. The isotope groups with statistically significant different areas (P <0.01) between the two groups were used to produce the accurate m/z values for directed acquisition of tandem mass spectra to sequence the peptide and identify the protein differences between the two groups. Among the proteins that were found to be increased in the tumor bearing urine (after excluding the hepatic-derived and well-recognized blood proteins e.g. albumin, hemopexin, hemoglobin) were meprin, E-cadherin, hyaluronan receptor, glycam, retinoblastoma binding protein.